1. Field of the Invention
The present invention relates to a method of performing contrast enhancement for an image photographed by a digital camera or read out from a storage medium by using a hyperbolic tangential function curve. More particularly, according to the present invention, the mean luminance value is calculated with respect to an image that is read, the type of the image is determined based on the mean luminance value, a contrast reference curve is created by applying a hyperbolic tangential function curve according to the type of the image, and the contrast of the image is enhanced by using the contrast reference curve.
2. Description of the Related Art
Contrast refers to a visual property to distinguish between an object and a background in an image. Since the eyes of a person are different from an optical sensor of a digital camera, if the person views an image which is photographed by a digital camera and not subject to image processing, the person may recognize the image as a blurred image. In this regard, if the contrast of the image is changed suitably for the eyes of the person through the image processing, a superior image suitable for the eyes of the person can be created.
Recently, there are many algorithms to solve the problems related to the contrast of images photographed under different lighting conditions such as bright, dark, and back lighting conditions. However, most of the algorithms have a problem in accuracy, or are very complex, so that the algorithms cannot be easily applied to a portable digital camera or a cellar phone equipped with a camera.